Time-dependent density functional theory study of the X-ray emission spectroscopy of amino acids and proteins

Abstract

The non-resonant X-ray emission spectroscopy of amino acids and a dipeptide have been studied using time-dependent density functional theory (TDDFT) calculations at the nitrogen and oxygen K-edges. Comparison with higher level calculations and experimental data shows that TDDFT with the CAM-B3LYP exchange–correlation functional and (Z+1)6-311G* basis set provides an accurate description of the spectra. Calculations for model α-helix and β-sheet structures show the spectra to relatively insensitive to the structure of peptide bond, with the greatest variation observed at the oxygen K-edge.